Projected project: The polymerase chain reaction (PCR)is a laboratory procedure being utilized increasingly as a diagnostic aid for microbial infections in which the causative agent cannot be grown or is present in very tiny amounts. PCR methodology has been described for leishmanial parasites which permit not only demonstration of presence of the parasite, but also the species of parasite of which there are multiple types. A project is planned to utilize PCR techniques on specimens obtained from known or suspected leishmanial patients referred to and seen at the Clinical Center over the next 2-3 years under Protocol No. 01-1-0238. In addition PCR will be used to analyze cryopreserved specimens from patients with unusual clinical presentations, and from patients whose infecting organism could not readily be classified.